A band stop filter eliminates a band of frequencies by using a low-pass filter to allow only low frequencies and a high-pass filter to allow only high frequencies. The outputs of the low-pass and high-pass filters are amplified and summed to restrict signals in the stopband while allowing signals around it. Band stop filters are used in applications like Raman spectroscopy and live sound processing to affect only a narrow frequency range. They work in the opposite way of band-pass filters by rejecting frequencies in the stopband rather than passing them.

1. Band Stop Filter Design
Definition:
• Eliminate band of frequencies
• Restricts frequencies inside the stopband
• Allow frequencies around stopband.
• Passes most frequencies unaltered
• Lessens high frequencies

2. Construction
Consists of:
Low-Pass Filter
Allows only low frequencies
High-Pass Filter
Allows only high frequencies
Amplifier, Op-amp and BJT
Amplify signals from low-pass and
high-pass filters

3. Scope:
Narrow score filters are utilized in :
Raman spectroscopy
Live sound proliferation
Instrument enhancers
Affecting the remainder of the recurrence range
Different names incorporate :
band limit filter
T-indent filter
band-end filter
band-reject filter

4. Comparison with other filters
Band Stop Filter
Other filters make the frequencies
they yield
A band-pass filter admits
frequencies within a given band,
rejecting frequencies below it and
above it
The band-pass filters flows the
high-pass and low-pass filters in
series
Other Filters
They basically weaken the
frequencies in the passband
A stop-band filter does the
reverse, rejecting frequencies
within the band and letting
through frequencies outside it
The band stop filter involves the
high-pass and low-pass filters in
equal

5. Band Stop Filter Characteristics
• two passing bands and one stop band
• features are diametrically opposed to those of the Band Pass
• parallel connection of a high pass filter and an occasional pass filter
• The low frequency assigned to the low pass filter
• The high frequency assigned to the high pass filter
• At extremely high and extremely low frequencies, the band stop filter circuit behaves like
an open circuit
• At intermediate frequencies, the circuit behaves like a short circuit.

6. Calculations:
Finding RLP
from the Low pass filter using formula:
Finding RHP
from the High pass filter using formula:

7. Calculations:

8. Design Components
Figure 1: Band Stop Filter Circuit
The transformation of filter in figure 1 is implemented using:
• A single low pass circuit
• A high pass filter circuits
• That are isolated from each other by
non-inverting voltage follower
• Output from these two filter circuits is then
summed using a third operational amplifier
connected as a voltage summer (adder)
Components used in building the Figure 1 and their values:

9. Graphs showing the magnitude and the part vs frequency of a particular network created with the ALICE desktop software
suite .
Graph:

10. Conclusion:
• The Band Stop Filter consists of two pass bands and one stop band
• It uses a high-pass filter and a low-pass filter that is connected in
parallel
• The lower and upper cut off frequencies of the filter depend on the
design of the filter.
• The bandwidth of the filter is nothing but a bandwidth filter
• When the Q factor is high the width of the notch response is small
• This is very popular in communication circuits

11. Thank You